Structured polarizer and method for making the same

ABSTRACT

A structured polarizer (linear polarizing filter) with side-by-side in a plane (lateral) regions having different polarization directions, complete extinction and complete transparency, is presented with two superpositioned planes (polarizers) with a polarizer whose surface can be structured. The polarization properties of a plane is structured in such a way and the planes are mutually oriented in such a way that polarizing regions with different polarization directions and/or polarization properties, such as contrast, polarization-direction-dependent absorption properties as a function of the wavelength, and/or non-polarizing regions, such as transparent or opaque and/or regions having a predefined absorption for specified wavelengths are obtained.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a structured polarizer (linearpolarizing filter) and a method for making the same.

[0003] 2. Description of the Related Art

[0004] A method is known from DE 195 23 257 A1 for producing a definedpermanent change of the extinction spectrum of a dielectric materialscontaining metal particles by intense laser pulses, which method can beused to produce structured polarizers.

[0005] The method is based on silver-containing glasses which areirradiated with a femtosecond laser, whereby the thereby produced formedsilver particles, which are responsible for the polarization, areoriented according to the polarization direction of the laser beam.

[0006] This method can be used to produce juxtaposed regions withdifferent polarization directions, however, due to the lack of suitablelasers only for very small structures. The achievable optical densities,i.e., the degrees of polarization, are also limited. The proposed methodis not capable to produce regions with complete extinction or completetransparency.

SUMMARY OF THE INVENTION

[0007] It is an object of the invention to describe a structuredpolarizer (linear polarizing filter) and a method for its manufacturewhich avoid the disadvantages of the present state of the technology,wherein (lateral) juxtaposed regions with different polarizationdirections, complete extinction and complete transparency, are to bearranged in a plane of the polarizer.

[0008] This object is solved by a structured polarizer with thecharacterizing features of claim 1 and by a method with thecharacterizing features of claim 12.

[0009] The structured polarizer (linear polarizing filter) is thereforecharacterized in that at least two superpositioned planes (polaizers)are formed with at least one polarizer whose surface can be structured,whereby the polarization properties of at least one of the planes arestructured in such a way and the planes are mutually oriented in such away that polarizing regions with different polarization directionsand/or polarization properties, such as contrast,polarization-direction-dependent absorption properties as a function ofthe wavelength, and/or non-polarizing regions, such as transparent oropaque and/or regions having a predefined absorption for specifiedwavelengths are obtained.

[0010] The method according to the invention is characterized in that atleast two linear polarizing filters (polarizers) with at least onepolarizing layer, which is disposed proximate to the surface and can bestructured, are structured through local thermal relaxation and/orthrough lithographic and etching processes, that subsequently these atleast two polarizing filters are exactly aligned relative to each otheraccording to the structure and assembled in such a way that an opticalcomponent is produced which has defined optical transparent and/oroptically opaque and/or polarizing regions with different polarizationdirections and/or polarizing properties.

[0011] With the present invention, a structured polarizer can berealized which has in one plane juxtaposed regions of differentpolarization directions, regions of maximum polarization at differentwavelengths with an identical or different polarization directions,regions without polarizing capability and regions with strongabsorption.

[0012] The lateral shape of the regions is thereby arbitrary, thegeometric dimensions can also be in the micrometer range.

[0013] Advantageous embodiments of the invention are described in thedependent claims.

[0014] Other objects and features of the present invention will becomeapparent from the following detailed description considered inconjunction with the accompanying drawings. It is to be understood,however, that the drawings are intended solely for purposes ofillustration and not as a definition of the limits of the invention, forwhich reference should be made to the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In the drawings, wherein like reference numerals delineatesimilar elements throughout the several views:

[0016]FIG. 1 a schematic diagram of different possible structures of apolarizer,

[0017]FIG. 2 a schematic diagram of a structured polarizer having a ringstructure,

[0018]FIG. 3 a schematic diagram of the application of the method of theinvention in a first embodiment,

[0019]FIG. 4 a schematic diagram of the application of the method of theinvention in a second embodiment with three planes,

[0020]FIG. 5 a schematic diagram of the application of the method of theinvention in a third embodiment for producing dichroic structures,

[0021]FIG. 6 the principle of thermal relaxation, and

[0022]FIG. 7 a schematic diagram of the application of the method of theinvention in a fourth embodiment as a wavelength-selective structuredpolarizing filter.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

[0023] Polarizers which are structured to have juxtaposed regions withdifferent a polarization directions, polarizing regions alternating withnon-polarizing regions, or with polarizing regions with complete and/orwavelength-selective absorption and capable of having arbitrarystructural dimensions down to the micrometer range, have so far not berealized with known technologies and with reasonable expenditures.

[0024] While crystal polarizers and prism polarizers cannot bestructured in this manner, such polarizers could be implemented with acomplex technology using foil polarizers or glass polarizers by placingsmall customized pieces of polarizing material side-by-side in asuitable manner. Such polarizers are described in WO 99/08081.Structures with a large number of pixels are too expensive and theattainable resolution is poor.

[0025] The structured polarizer according to the present inventionincludes a combination of two polarizers, which are structured orconnected to each other by locally introducing energy and/or by alocally removing the polarizing layer proximate to the surface, so thatthe polarizing layers near the surface are joined directly with opticalcements.

[0026] The desired angle between the polarization directions of adjacentregions is determined by the angle, by which the two polarizers arerotated relative to each other. Since the polarizing surfaces aredirectly abutting each other and have a thickness of approximately one□m, the polarizers operate essentially without parallax.

[0027] By eliminating parallax, several structured polarizers of theaforedescribed type can be combined with each other, whereby therelative angles of the polarization directions between the polarizerscan be arbitrary.

[0028] Starting materials for producing the polarizers according to thepresent invention are polarizers whose polarizing layer is located in aregion proximate to the surface, i.e., within only micrometers of thesurface. Such polarizers are described in Cornelius, H.-J., Heine, G.,Volke, A.: “Paper 9th Triennial ITG Conference on Displays and VacuumElectronics”: “Dichroic Polarizers Based on Glass”, May 2-3, 2001, andin the 12. Conference Volume of Electronic Displays '97, pp. 104-110.These are dichroic glass polarizers whose optical properties are locatedat the surface. According to the methods described herein, colloidalsilver is produced in a region close to the surface of a sodium-silicateglass of conventional quality by exchange of the sodium ions with silverions and subsequent reduction annealing. By tensile deformation of theglass at temperatures above T_(g), the silver particles aresimultaneously deformed in the direction of the applied tensile stress.The deformed silver particles are responsible for the polarizingproperties of the glass. The wavelength of maxiinum polarization dependson the degree of deformation of the silver particles, and the degree ofpolarization depends on the density and the quantity of the stretchedsilver particles. The deformation of the particles can be relaxed byapplying energy after the deformation. The degree of the relaxationdepends on the duration and the magnitude of the applied energy, whichcan be increased to a point where the un-deformed initial state isreached. By applying the energy locally, the material can be structuredinto regions having maximum polarization at different wavelengths. Inthis way, the orientation of the particles and therefore also thedirection of the polarization are always maintained. Laser and electronbeams have proven to be suitable means for locally applying energy.

[0029] Such silver-containing unstructured and structured polarizers aremanufactured by the applicant under the trademark colorPol and are usedin the following embodiments.

[0030]FIGS. 1 and 2 illustrate possible structures that can be producedwith the method of the invention, which have arranged juxtaposed regionsof different polarization directions, complete extinction and completetransparency.

[0031]FIG. 1 shows also the application of a black matrix 11, which canbe realized by structuring polarizing surfaces in such a way that thepolarizing regions with a 90° different polarization direction areconnected so that the regions of maximum extinction form a “matrix.”Another method which is applied in particular in situations wherepolarizers have their maximum polarization at different wavelengths, amatrix is applied on one or both polarizing surfaces by suitable methods(screen printing, evaporation). A variety of materials can be used:paint, chromium, aluminum and the like. After combining the at least twopolarizers, the black matrix 11 is arranged in the interior so that itis protected and parallax-free.

[0032]FIG. 2 shows a ring structure with a different polarizing regions.

[0033]FIG. 3 depicts a first specific embodiment of the invention.

[0034]FIG. 3 shows the basic possibilities of the application of themethod according to the invention with two polarizing filters 1, 2, witheach filter having a surface layer OS disposed of one side that producesthe polarization. Such surface layer OS can be produced, for example, byonly a using lithographic etch structuring process. The polarizingfilters 1, 2 are assembled into a component BE by rotating them 90°relative to each other so that the two polarizing surface layers OS arein direct contact with each other. The direct contact between thepolarizing layers OS eliminates parallax errors.

[0035] The form of the structures (micro and macro region) can bearbitrarily selected, and the following four combinations are possiblewhen the polarization directions of the regions relative to each otherare arranged at an angle of 90°:

[0036] transparent (both polarizing layers OS removed)

[0037] opaque (none of the polarizing layers OS removed)

[0038] horizontally polarizing (layer OS of the upper polarizer 1removed)

[0039] vertically polarizing (layer OS of the lower polarizer 2 removed)

[0040] For realizing different absorption characteristics (opticaldensities), the layer OS in the different regions can also be onlypartially removed. But this partial removal weakens the absorptivity,which produces different (smaller) contrast ratios, but in generalproduces higher transmission values, for both vertically andhorizontally polarized light.

[0041] The second embodiment of FIG. 4 illustrates three planes 3 to 5(three structured polarizing filters) which are arranged at relativeangles of 60° and assembled to a component 8, which is advantageous, forexample, for sensor applications. A small parallax can be achieved inspite of the three planes 3 to 5, if the intermediate substrate 7 whichhas at least one active polarizing surface layer 6 has a reducedthickness d.

[0042] The resulting component 8 is a polarizing filter with threepolarizing annular segments which have polarization directions that aremutually offset by 60°.

[0043] The third embodiment of FIG. 5 shows an application for producingdichroic structures in situations where the polarization manifestsitself only in certain spectral regions and the wavelength at which thisregion is located can be locally changed. In this embodiment, thelocation is actively changed by displacing the absorption bands throughlocal thermal relaxation (FIG. 6), for example with an electron beam, ofthe non-spherical (ellipsoidal) colloidal metal particles, which causethe absorption and are embedded in the surface of the carrier matrix,for example glass, to assume a more spherical form Alternatively, eachof the two components can also be a structured polarizing filteraccording to the aforedescribed invention, whereby the parallax isdetermined by the thickness of the inner carrier substrate.

[0044] The fourth embodiment depicted in FIG. 7 is awavelength-selective structured polarizing filter and is made preferablyof two dichroic glass polarizers 10, 9 which are structured by astructuring technology (preferably a stripe structure produced by localthermal relaxation with an electron beam or laser and a quadrantstructure produced by photolithography and etching), so as to producethe required properties at the desired wavelength(s). The intentionalchange in the polarization properties is based on the observation thatthe polarization is produced by uniaxially stretched and uniformlyoriented particles in a dielectric environment, which in the employeddichroic glass polarizer is preferably colloidal silver in glass. Whenenergy is applied to the glass or the glass is heated, the embeddedellipsoidal colloidal particles relax into a spherical shape. Thisprocess is accelerated by increasing the temperature which lowers theviscosity of the glass. This relaxation process can be controlled bysuitable methods (electron beam technology and technology) so that therelaxation process can be stopped at any point between the initialeccentricity and the spherical shape (by adjusting time and energy).Since the eccentricity of the colloidal particles determines thepolarization-direction-dependence of the absorption (see FIG. 6) and alocal heat treatment with relaxation is possible, thepolarization-direction-dependent absorption properties can be laterallystructured. Such a method is conventional and described in DE 196 42116.

[0045] Thus, while there have been shown and described and pointed outfundamental novel features of the invention as applied to a preferredembodiment thereof, it will be understood that various omissions andsubstitutions and changes in the form and details of the devicesillustrated, and in their operation, may be made by those skilled in theart without departing from the spirit of the invention. For example, itis expressly intended that all combinations of those elements and/ormethod steps which perform substantially the same function insubstantially the same way to achieve the same results are within thescope of the invention. Substitutions of elements from one describedembodiment to another are also fully intended and contemplated. It isalso to be understood that the drawings are not necessarily drawn toscale but that they are merely conceptual in nature. It is theintention, therefore, to be limited only as indicated by the scope ofthe claims appended hereto.

What is claimed is:
 1. A structured polarizer (linear polarizingfilter),wherein at least two superpositioned planes (polarizers) with atleast one polarizer whose surface can be structured are formed, wherebythe polarization properties of at least one of the planes are structuredin such a way and the planes are mutually oriented in such a way thatpolarizing regions with different polarization directions and/orpolarization properties, such as contrast,polarization-direction-dependent absorption properties as a function ofthe wavelength, and/or non-polarizing regions, such as transparent oropaque and/or regions having a predefined absorption for specifiedwavelengths are obtained.
 2. The structured polarizer according to claim1, wherein two planes are provided with polarization directions that aremutually offset by 90 degrees, with the surface of the planes containingpolarization-effecting layers that can be locally removed and/or locallystructured with respect to their polarization properties, such aspolarization-direction dependent absorption characteristics as afunction of the wavelength.
 3. The structured polarizer according toclaim 1, wherein at least one of the polarizers (planes) with respect toits optical properties, such as location of maximum absorption, isarbitrarily structured by a structuring method, such as local thermalrelaxation with an electron beam or a laser or by lithographic andchemical etching processes, such as wet etching or plasma etching, bylocal removal of the at least one polarizing surface layer.
 4. Thestructured polarizer according to claim 1, wherein at least one of thepolarizers (planes) is arbitrarily structured by lithographic andchemical etching processes, such as wet etching or plasma etching, bylocal removal of the at least one polarizing surface layer.
 5. Thestructured polarizer according to claim 1, wherein the polarizingsurface layers of two polarizers (planes) are arranged and joined insuch a way that no noticeable parallax errors are produced.
 6. Thestructured polarizer according to claim 1, wherein more than twopolarizers (planes) are superpositioned so as to form structures withmore than two polarization directions.
 7. The structured polarizeraccording to claim 6, wherein three polarization directions which arerotated relative to each other by 60° can be realized.
 8. The structuredpolarizer according to the claim 1, wherein the structures are formed tothe micrometer range.
 9. The structured polarizer according to claim 1,further comprising a “black matrix.”
 10. A method for producing astructured polarizer, wherein at least two linear polarizing filters(polarizers) with at least one polarzing layer, which is disposedproximate to the surface and can be structured, are structured throughlocal thermal relaxation and/or through lithographic and etchingprocesses, that subsequently these at least two polarizing filters areexactly aligned relative to each other according to the structure andassembled in such a way that an optical component is produced which hasdefined optical transparent and/or optically opaque and/or polarizingregions with different polarization directions and/or polarizingproperties.
 11. The method according to claim 10, using glass polarizerswhose optical properties are located at the surface, such as colorPolpolarizing filters, which are structured by an electron beam or a laserand/or by lithographic and etching methods while maintaining theoriginal polarization direction, and which are oriented relative to eachother by positioning markers and mask aligner and combined into thecomponent by gluing.
 12. The method according to the claims 10,employing photoresist masking for structuring conventional semiconductormanufacturing methods.
 13. The method according to claim 10, employingan electron beam for structuring which locally changes the polarizationproperties through thermal relaxation.
 14. The method according to claim10, employing for structuring a laser locally changes the polarizationproperties through thermal relaxation.
 15. The method according to claim11, wherein a UV-hardening adhesive is used for assembly, which ishardened by irradiation with UV light after the at least two polarizingfilters have been positioned.
 16. The method according to claim 11,wherein the adhesive used for assembly is a thermo-setting adhesivewhich hardens by applying a temperature after the at least twopolarizing filters have been positioned.
 17. The method according toclaim 11, wherein the adhesive used for assembly is a two-componentadhesive which hardens by a chemical reaction after the at least twopolarizing filters have been positioned.
 18. The method according toclaim 11, wherein glass is used for assembly which, after the at leasttwo polarizing filters have been positioned, establishes the connectionat a lower temperature than the destruction temperature of the employedpolarizers.
 19. The method according to the claims 10, whereinmanufacture is done in a matrix, which is subsequently separated bymethods such as wafers sawing, ultrasound drilling, so than positioningmarkers are not part of the structured polarizing filter.
 20. The methodaccording to claim 10, wherein at least one of the polarizers (planes)comprises an additional “black matrix.”
 21. The method according toclaim 11, wherein the “black matrix” is produced by suitable structuringof the polarizing surfaces due to the resulting absorption when the twopolarizers to be joined are rotated by 90 degrees.